Online event registration : Display name is replaced with email address if name fields are not collected in a profile

When an existing contact registers for an event online - using a simple online registration form (free event, no profile) - the code is setting the contact Display Name to the email address entered by the user. The existing Display Name is over-written.

This is incorrect behavior for cases where there is already a display name stored for the matched contact record.

NOTE: We are NOT over-writing or clearing the existing name fields - so if the contact record is edited and saved, the display name is restored to it's "correct" value. However, this can still be quite confusing for users - and should be fixed.